Appropriate control methods for mobile virtual exhibitions

It is becoming popular to render art exhibitions in Virtual Reality (VR). Many of these are used to deliver at-home experiences on peoples’ own mobile devices, however, control options on mobile VR systems are necessarily less flexible than those of situated VR fixtures. In this paper, we present a study that explores aspects of control in such VR exhibitions - specifically comparing ‘on rails’ movement with ‘free’ movement.We also expand the concept of museum audio guides to better suit the VR medium, exploring the possibility of embodied characterguides. We compare these controllable guides with a more traditional audio-guide. The study uses interviews to explore users’ experience qualitatively, as well as questionnaires addressing both user experience and simulator sickness. The results suggest that users generally prefer to have control over both their movement and the guide, however, if relinquishing movement control, they prefer the uncontrolled guide. The paper presents three key findings: (1) users prefer to be able to directly control their movement; (2) this does not make a notable difference to simulator sickness; (3) embodied guides are potentially a good way to deliver additional information in VR exhibition settings

How Structure Determines Correlations in Neuronal Networks

Networks are becoming a ubiquitous metaphor for the understanding of complex biological systems, spanning the range between molecular signalling pathways, neural networks in the brain, and interacting species in a food web. In many models, we face an intricate interplay between the topology of the network and the dynamics of the system, which is generally very hard to disentangle. A dynamical feature that has been subject of intense research in various fields are correlations between the noisy activity of nodes in a network. We consider a class of systems, where discrete signals are sent along the links of the network. Such systems are of particular relevance in neuroscience, because they provide models for networks of neurons that use action potentials for communication. We study correlations in dynamic networks with arbitrary topology, assuming linear pulse coupling. With our novel approach, we are able to understand in detail how specific structural motifs affect pairwise correlations. Based on a power series decomposition of the covariance matrix, we describe the conditions under which very indirect interactions will have a pronounced effect on correlations and population dynamics. In random networks, we find that indirect interactions may lead to a broad distribution of activation levels with low average but highly variable correlations. This phenomenon is even more pronounced in networks with distance dependent connectivity. In contrast, networks with highly connected hubs or patchy connections often exhibit strong average correlations. Our results are particularly relevant in view of new experimental techniques that enable the parallel recording of spiking activity from a large number of neurons, an appropriate interpretation of which is hampered by the currently limited understanding of structure-dynamics relations in complex networks

Activity in a premotor cortical nucleus of zebra finches is locally organized and exhibits auditory selectivity in neurons but not in glia

Motor functions are often guided by sensory experience, most convincingly illustrated by complex learned behaviors. Key to sensory guidance in motor areas may be the structural and functional organization of sensory inputs and their evoked responses. We study sensory responses in large populations of neurons and neuron-assistive cells in the songbird motor area HVC, an auditory-vocal brain area involved in sensory learning and in adult song production. HVC spike responses to auditory stimulation display remarkable preference for the bird's own song (BOS) compared to other stimuli. Using two-photon calcium imaging in anesthetized zebra finches we measure the spatio-temporal structure of baseline activity and of auditory evoked responses in identified populations of HVC cells. We find strong correlations between calcium signal fluctuations in nearby cells of a given type, both in identified neurons and in astroglia. In identified HVC neurons only, auditory stimulation decorrelates ongoing calcium signals, less for BOS than for other sound stimuli. Overall, calcium transients show strong preference for BOS in identified HVC neurons but not in astroglia, showing diversity in local functional organization among identified neuron and astroglia populations

Doença celíaca associada à tireoidite de Hashimoto e síndrome de Noonan Celiac disease associated with Hashimoto's thyroiditis and Noonan syndrome

OBJETIVO: Relatar o caso clínico de uma criança portadora de doença celíaca, tireoidite de Hashimoto e síndrome de Noonan. DESCRIÇÃO DE CASO: Menina de dez anos e seis meses, branca, apresentando história de diarreia líquida há cinco meses e "aumento da barriga". Ao exame, mostrava peso de 20.580g (p<3), estatura de 114cm (p<3), hidratada, descorada 2+/4+ e consciente. Presença de fácies triangular, com hipertelorismo ocular aparente, posição antimongoloide das fendas palpebrais, orelhas em abano de baixa implantação, micrognatia, pescoço curto e pectus excavatum. O abdome mostrava-se globoso, flácido, indolor, com hérnia umbilical, fígado a 2cm do rebordo costal direito, linfedema em membro superior direito e edema de membros inferiores. Nos exames subsidiários, havia anemia microcítica e hipocrômica, déficit de proteínas totais, tireoidite de Hashimoto e atraso de cinco anos na idade óssea. Na ultrassonografia abdominal, as alças intestinais estavam levemente dilatadas. Devido ao linfedema e à diarreia crônica, a hipótese inicial foi de linfangiectasia intestinal, confirmada pela biópsia jejunal, que ainda mostrou padrão compatível de doença celíaca. O cariótipo foi 46XX com diagnóstico clínico de síndrome de Noonan. COMENTÁRIOS: As doenças autoimunes se associam; no caso apresentado, a doença celíaca se associou à tireoidite de Hashimoto, possivelmente pela presença de antígenos do sistema HLA. Já a associação de doença celíaca à síndrome de Noonan é muito rara, sendo este o terceiro relato na literatura.<br>OBJECTIVE: To describe the clinical case of a child with celiac disease, Hashimoto's thyroiditis and Noonan syndrome. CASE DESCRIPTION: A Caucasian girl aged ten years and six months had liquid diarrhea for five months, and a "distended belly". At the physical exam: weight of 20,580g (p<3), length of 114cm (p<3), hydrated, anemic 2+/4+ and conscious. The patient presented triangular facies, apparent ocular hypertelorism, antimongoloid position of the palpebral fissures, ears with low implantation, micrognathia, short neck and pectus excavatum. The abdomen was globular, flaccid and painless; the liver was 2cm below the right costal margin. Lymphedema in right upper limb and lower limb edema was also noted. Laboratory exams showed microcytic and hypochromic anemia, deficit of total proteins, Hashimoto's thyroiditis and a 5-year delay in bone age. Abdominal ultrasonography showed the bowel slightly dilated. Due to lymphedema and chronic diarrhea, the initial hypothesis was intestinal lymphangiectasis, which was confirmed by a jejunal biopsy, which also showed celiac disease. The genetic evaluation revealed a 46XX karyotype and a clinical diagnosis of Noonan syndrome. COMMENTS: Different autoimmune diseases can be associated. In this case, the celiac disease and the Hashimoto's thyroiditis are possibly related to the presence of HLA system antigens. However, the association of the celiac disease with the Noonan syndrome is very rare, and this is the third report in the literature

Differential connectivity and response dynamics of excitatory and inhibitory neurons in visual cortex

Neuronal responses during sensory processing are influenced by both the organization of intracortical connections and the statistical features of sensory stimuli. How these intrinsic and extrinsic factors govern the activity of excitatory and inhibitory populations is unclear. Using two-photon calcium imaging in vivo and intracellular recordings in vitro, we investigated the dependencies between synaptic connectivity, feature selectivity and network activity in pyramidal cells and fast-spiking parvalbumin-expressing (PV) interneurons in mouse visual cortex. In pyramidal cell populations, patterns of neuronal correlations were largely stimulus-dependent, indicating that their responses were not strongly dominated by functionally biased recurrent connectivity. By contrast, visual stimulation only weakly modified co-activation patterns of fast-spiking PV cells, consistent with the observation that these broadly tuned interneurons received very dense and strong synaptic input from nearby pyramidal cells with diverse feature selectivities. Therefore, feedforward and recurrent network influences determine the activity of excitatory and inhibitory ensembles in fundamentally different ways